In measuring sensors that are exposed to the exhaust gas of internal combustion engines, during driving operation, as a result of combustion residues and compounds contained in the exhaust gas, such as heavy metals, for example, lead, manganese, zinc, cadmium, magnesium, cerium, phosphorus, silicon, which originate with additives or residual pollutants in fuels, lubricating oils and gaskets of the internal combustion engine, deposits form on the sensor element which, in the long run, lead to glazing or clogging of the diffusion barrier and protective layers or to poisoning, that is, passivating of the catalytic activity, of the electrodes of the sensor element. The so-called contamination of the measuring sensor interferes with the function of the sensor element, since the electrodes preferably made up of platinum or platinum alloys lose their catalytic function.
In order to counter the so-called probe contamination due to lead residues, in one known measuring sensor of this type, (European Patent No. 0 159 905) the outer element of the sensor element is coated with a protective lining made up of a heat-resistant metal oxide, in which the lead-trapping, stable metals from the group platinum, ruthenium, paddaium, nickel, gold and alloys of the same are uniformly distributed.